#10045 HIGH 1.5-sof: XO-1.5 Record audio/video are out of sync with each other

[John Watlington]

Reading the patch, it sounds like a better set of parameters
to try would be:
vm.dirty_background_ratio=10
vm.dirty_bytes=90

Cheers,
wad

On May 11, 2010, at 10:41 PM, James Cameron wrote:

> On Tue, May 11, 2010 at 10:16:13PM -0400, Martin Langhoff wrote:
>> What you are saying is that this is a different issue from what dsd
>> tracked down -- entirely possible that these are 2 orthogonal issues.
> 
> Yes, entirely possible.
> 
>> Does the frequency and/or std deviation change if you tweak the
>> vm.dirty_* sysctl values?
> 
> Yes, significantly.  What I've observed is most likely entirely due to
> vm.dirty_* behaviour.
> 
> The default on os123 is
> 
> vm.dirty_background_bytes=0
> vm.dirty_background_ratio=10
> vm.dirty_bytes=0
> vm.dirty_expire_centisecs=3000
> vm.dirty_ratio=20
> vm.dirty_writeback_centisecs=500
> 
> Changing this to
> 
> vm.dirty_background_ratio=90
> vm.dirty_expire_centisecs=60000
> vm.dirty_ratio=90
> vm.dirty_writeback_centisecs=0
> 
> causes the dd to finish in 7 seconds instead of 92 seconds, the sync to
> take much longer, and the write latencies are much smaller.
> 
> So the effect I was seeing was documented ... "process which is
> generating disk writes will itself start writing out dirty data.", per
> vm.txt in Documentation/
> 
> -- 
> James Cameron
> http://quozl.linux.org.au/